ExampleOutput.txt

msg: MsgOne {}
uuid: '336228ee-b2e8-4c78-acf4-a8302125552b'
(MSG-ONE:336228ee-b2e8-4c78-acf4-a8302125552b)-|
msg: MsgTwo {}
uuid: 'cbfeae0b-11f1-4e58-a4f9-35bab61bdbf2'
uuid: '7965f57f-cde5-4ca5-8377-bd03b9c71784'
(MSG-TWO:7965f57f-cde5-4ca5-8377-bd03b9c71784)-(MSG-ONE:cbfeae0b-11f1-4e58-a4f9-35bab61bdbf2)-|
msg: MsgTwo {}
uuid: '256702ea-6702-4aa2-84c0-3977e1763e8'
uuid: 'fd7bdf0d-6f6b-46d2-b394-f268c4c5a473'
uuid: '2bea4621-873a-47f5-9803-0da53e5dc34f'
(MSG-TWO:2bea4621-873a-47f5-9803-0da53e5dc34f)-(MSG-TWO:fd7bdf0d-6f6b-46d2-b394-f268c4c5a473)-(MSG-ONE:256702ea-6702-4aa2-84c0-3977e1763e82)-|

TestMUV.purs

module TestMUV where

import Prelude

import Effect (Effect)
import Effect.Class (liftEffect)
import Effect.Console (log)
import Data.Either (Either, either)
import Control.Monad.Except.Trans (ExceptT, runExceptT)

import FRP.Event (Event)
import FRP.Event as Event

import Debug.Trace as DT

import UUID as UUID

data Error = Error String

type Program a = ExceptT Error Effect a


data Msg = MsgOne | MsgTwo


instance showMsg :: Show Msg where
    show MsgOne = "MSG-ONE"
    show MsgTwo = "MSG-TWO"


runMUV
    :: forall model view
     . Event Msg
    -> Program model
    -> (Msg -> Program model -> Program model)
    -> (Either Error model -> view)
    -> Event (Effect view)
runMUV messages init userUpdate userView =
    let
        updates = Event.fold update messages init
        views = view <$> updates
    in views
    where
        update :: Msg -> Program model -> Program model
        update msg model =
            let _ = DT.spy "msg" msg
            in userUpdate msg model
        view :: Program model -> Effect view
        view program =
            userView <$> runExceptT program


main :: Effect Unit
main = do
    { event : messages, push } <- Event.create
    let views = runMUV messages (pure "|") update view
    _ <- Event.subscribe views \effV -> effV >>= log
    push MsgOne
    push MsgTwo
    push MsgTwo
    pure unit
    where
        update msg model =
            model >>= \prev -> do
                uuid <- liftEffect UUID.new
                let _ = DT.spy "uuid" uuid
                pure $ "(" <> show msg <> ":" <> UUID.toString uuid <> ")-" <> prev
        view errOrModel =
            either (const "ERR") identity errOrModel

UUID.js

"use strict";

/**
 * Fast UUID generator, RFC4122 version 4 compliant.
 * @author Jeff Ward (jcward.com).
 * @license MIT license
 * @link http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/21963136#21963136
 **/
var UUID = (function() {
    var self = {};
    var lut = []; for (var i=0; i<256; i++) { lut[i] = (i<16?'0':'')+(i).toString(16); }
    self.generate = function() {
      var d0 = Math.random()*0xffffffff|0;
      var d1 = Math.random()*0xffffffff|0;
      var d2 = Math.random()*0xffffffff|0;
      var d3 = Math.random()*0xffffffff|0;
      return lut[d0&0xff]+lut[d0>>8&0xff]+lut[d0>>16&0xff]+lut[d0>>24&0xff]+'-'+
        lut[d1&0xff]+lut[d1>>8&0xff]+'-'+lut[d1>>16&0x0f|0x40]+lut[d1>>24&0xff]+'-'+
        lut[d2&0x3f|0x80]+lut[d2>>8&0xff]+'-'+lut[d2>>16&0xff]+lut[d2>>24&0xff]+
        lut[d3&0xff]+lut[d3>>8&0xff]+lut[d3>>16&0xff]+lut[d3>>24&0xff];
    }
    return self;
})();

exports.newAsString = function() {
    return UUID.generate();
}

UUID.purs

module UUID
    ( UUID
    , new
    , toString
    ) where


import Prelude
import Data.Maybe (Maybe(..))
import Effect (Effect)


foreign import newAsString :: Effect String


newtype UUID = UUID String

derive instance eqUuid :: Eq UUID
derive instance ordUuid :: Ord UUID


new :: Effect UUID
new = newAsString <#> UUID


toString :: UUID -> String
toString (UUID uuid) = uuid


instance showUUID :: Show UUID where
  show (UUID uuid) = "{" <> uuid <> "}"